FORMER Sunshine Coast man Henri van Breda axed his family to death, smoked three cigarettes and then rang his 16-year-old girlfriend - even as his teenage sister lay bleeding from massive head wounds and fighting for her life, a South African court has been told.

Prosecution closing arguments in the gripping murder trial of the 23-year-old at Western Cape High Court painted a picture of a callous and calculating killer, who butchered his mother, father and brother before making a call to emergency services so calm the operator thought it was a prank.

He was 20 at the time of the incident in the family home in an exclusive golf estate in Stellenbosch in January 2015.

He concocted a story she said was "well rehearsed" by the time he came to court.

The van Breda family in happier times.
Photo: ContributedContributed

Mr van Breda blamed a laughing, balaclava-clad intruder, whom he thought was black, for attacking his family as he watched helplessly from a bathroom.

He described how he struggled with the attacker, disarmed him and threw the axe at him, before losing consciousness.

But Ms Galloway said that account did not tally with his demeanour when emergency services arrived at the house, which "was calm enough to direct them up the stairs and was not unfocused and distraught".

"This was not consistent with a house robbery or armed robbery," Ms Galloway said.

None of the victims made an attempt to hide or call for help ... that is because the attacker was known to them."

The attacker could only have been Mr van Breda, she said.

That Marli, a former Matthew Flinders College student, survived was "not indicative of a lesser attack, but rather a miracle", Ms Galloway said.

Picking apart the defence case, which included a claimed late diagnosis of epilepsy which Mr van Breda's lawyers said accounted for a missing 160 minutes in his timeline, Ms Galloway paid attention to Mr van Breda's wounds. Scratch marks on his arms, equal in depth and almost perfectly parallel, were labelled "textbook" examples of those appearing to be self-inflicted.

MIRACLE: Prosecutor Susan Galloway says it was a miracle Marli van Breda survived the attack that left her parents and one of her brothers dead.Contributed

Asked by Judge Siraj Desai what it would mean if Mr van Breda had cut himself, Ms Galloway was unequivocal.

"The version of an intruder loses all credibility," she said.

Mr van Breda has pleaded not guilty to three counts of murder and one of attempted murder.